Implantable devices that perform neuromodulation treatments are known. Most use large devices with batteries and long leads to electrically stimulate nerves inside the body. These devices require invasive implantation, which are very costly. They also require periodic battery replacement, which requires additional surgery. The large sizes of these devices and their high costs have prevented their use in a variety of applications that have demonstrated effective neurostimulation treatments.
Nerve stimulation treatments have shown increasing promise recently, showing potential in the treatment of many chronic diseases including drug-resistant hypertension, motility disorders in the intestinal system, metabolic disorders arising from diabetes and obesity, and chronic pain conditions among others. Many of these treatments have not been developed effectively because of the lack of miniaturization and power efficiency, in addition to other factors. Wirelessly powered systems with communication are desirable because they can be miniaturized and have no need for battery replacements. However, wireless systems have an even more restrictive power budget.
There have also been several attempts at developing miniature wireless implantable, neurostimulators, including the device described in U.S. Pat. No. 5,193,539. This device receives power wirelessly, configures stimulation, and performs electrical stimulation in a needle injectible form factor. However, the systems in place for power delivery are highly sensitive to placement and alignment, and offer limited bandwidth for data communications. The receiver operates at MHz frequencies through an inductive link, requiring multiple coils and ferrite cores. More recently, new neurostimulation devices have transitioned to operation at higher frequencies, though these devices presently rely on dipole antennas and struggle with data transfer because of challenges with high-frequency operation. Furthermore, these devices provide stimulation from directly rectifying the power waveform, reducing the precision of control and introducing additional complexity and overhead in the overall system. These systems also have limitations in the duration of pulses that can be delivered, and long pulses can be necessary to induce therapeutic effects for many applications, including gastric stimulation. These systems also rely on instantaneously received power to stimulate excitable tissue and do not aggregate received energy for use in therapy. Additionally, these systems do not provide for a way to use larger non-dipole antennas.